Email YOUR Questions directly to the Stream
Doctor. This is your opportunity to get an experts
professional opinion on anything stream related.

Q.
From aacfish: In your last column on FAOL you mentioned that
mayflies couldn't inflate their wings in the water column. Why not? I was under
the impression that some Heptagenia species actually emerged under water. Is
that an erroneous impression? I'm sure I've seen this in fly fishing books
somewhere.

A.
You asked two questions, but I'm going to answer
them in reverse order. First the question as to
whether mayflies can inflate their wings in the
water column; I'm afraid you've found some
misleading information. I spent the morning
consulting several books in my library about
aquatic insects (one just on mayflies) and found
no evidence in the life history descriptions of
mayflies that they inflated their wings prior
to reaching the water surface. To confirm this,
I phoned several aquatic entomologist colleagues
to see if any of them knew of any mayflies that
inflated their wings underwater. Nobody I
talked to knew of any evidence that mayflies
inflated their wings underwater; this is done
at the water/air interface or on land after they've
crawled out of the water.

Some adult female mayflies, especially in the genus
Baetis, reenter the water after mating by crawling
along rocks or twigs to deposit their eggs directly
onto the substrate. If one didn't know that the
mayflies had emerged prior to their underwater journey,
they might mistakenly infer that they had inflated
their wings and were just emerging. Once they deposit
their eggs, they do not reemerge into the air; they
die and become part of the drift.

If you can find the reference to this happening in
a fly fishing book, let me know the book's title; I'd
like to see it.

The "Why is that?" question is harder, if not impossible,
to answer. It may be related to physiological problems
in that they can't circulate blood (haemolymph) into
the new wing veins. Further, it would seem that
inflating the wings prior to reaching the surface
would be disadvantageous because (1) it would present
a larger morsel to predators, and (2) it would decrease
their ability to resist the current, thus probably
extending their time in the drift and susceptibility
to drift feeders. This is speculation; they don't inflate their
wings under water, but I'm not sure there is an answer to "why not."
~ C. E. (Bert) Cushing, aka Streamdoctor
105 W. Cherokee Dr.
Estes Park, CO 80517
Phone: 970-577-1584
Email: streamdoctor@aol.com

The 'Stream Doctor' is a retired professional stream ecologist and
author, now living in the West and spending way too much time
fly-fishing. You are invited to submit questions relating to
anything stream related directly to him for use in this Q & A Feature
at streamdoctor@aol.com.

If you would like to comment on this or any other article please feel free to
post your views on the FAOL Bulletin Board!